Method and apparatus for storing normally gaseous hazardous material in liquid phase

ABSTRACT

METHOD AND APPARATUS FOR SAFE VENTING OF VAPORS OF NORMALLY GASEOUS HAZARDOUS MATERIAL STORED IN LIQUID PHASE IN AN INSULATED CONTAINER UNDER LOW PRESSURE AND TEMPERATURE. HAZARDOAUS VAPOR IS WITHDRAWN FROM THE CONTAINER AT TIMES WHEN THE INTERNAL CONTAINER PRESSURE EXCEEDS A PREDETERMINED VALUE AND FED TO A ZONE CONTAINING A CATALYST TO OXIDIZE THE VAPOR TO A HARMLESS GAS WHICH IS VENTED TO THE ATMOSPHERE. IN THE EVENT THE CONTAINER INSULATION FAILS CAUSING RAPID VAPORIZATION OF STORED LIQUID, A LARGE QUANTITY OF HAZARDOUS VAPOR IS WITHDRAWN WHEN THE INTERNAL CONTAINER PRESSURE EXCEEDS A HIGHER PREDETERMINED VALUE AND FED TO A CATALYTIC ZONE OF GREATER CAPACITY WHICH MAY INCLUDE A PLURALITY OF CATALYTIC UNITS. THE INVENTION IS DISCLOSED IN THE ENVIRONMENT OF LIQUEFIED CARBON MONOXIDE AND HAZARDOUS VAPORS THEREOF BEING OXIDIZED CATALYTICALLY TO HARMLESS CARBON DIOXIDE.

Sept. 28, 1971 slNGLETON ETAL 3,608,324 I METHOD AND APPARATUS FOR STORING NORMALLY GASEOUS HAZARDOUS.MATERIAL IN LIQUID PHASE Filed June 4, 1969 FIG. 2

INVENTORS ALAN H.SINGLETON EDWARD G.BISKIS BY S ATTORNEY United States Patent 3,608,324 METHOD AND APPARATUS FOR STORING NOR- MALLY GASEOUS HAZARDOUS MATERIAL IN LIQUID PHASE Alan H. Singleton, Emmaus, Pa., and Edward G. Biskis,

Omaha, Nehru, assignors to Air Products and Chemicals, Inc., Allentown, Pa.

Filed June 4, 1969, Ser. No. 830,397 Int. Cl. F17c 13/00 US. CI. 62-48 11 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for safe venting of vapors of normally gaseous hazardous material stored in liquid phase in an insulated container under low pressure and temperature. Hazardous vapor is withdrawn from the container at times when the internal container pressure exceeds a predetermined value and fed to a zone containing a catalyst to oxidize the vapor to a harmless gas which is vented to the atmosphere. In the event the container insulation fails causing rapid vaporization of stored liquid, a large quantity of hazardous vapor is withdrawn when the internal container pressure exceeds a higher predetermined value and fed to a catalytic zone of greater capacity which may include a plurality of catalytic units. The invention is disclosed in the environment of liquefied carbon monoxide and hazardous vapors thereof being oxidized catalytically to harmless carbon dioxide.

BRIEF SUMMARY OF THE INVENTION This invention relates to improvements on methods of and apparatus for liquid phase storage and transportation of normally gaseous hazardous material.

Normally gaseous, hazardous materials, such as carbon monoxide, are transported in liquid phase at low temperature and pressure in double-walled container vehicles in which the space between the walls is filled with insulation material and maintained under vacuum to minimize heat flow into the container and resulting vaporization of the liquefied material. Since the insulation system does not provide a perfect heat barrier, the liquefied gas will vaporize and it is necessary to vent vapor from the container to prevent development of internal pressures in excess of the maximum operating design pressure of the container. Because of its hazardous nature, carbon monoxide vapor cannot be safely vented except at isolated areas and it may be necessary to deviate the transport from its scheduled route to effect safe venting in advance of the internal pressure of the container reaching its maximum operating design pressure. In addition, the insulation efliciency of double-walled containers depends upon the maintaining of a relatively high vacuum in the insulation space and, in the event the high vacuum is lost due to a leak in the outer wall for example, carbon monoxide liquid will vaporize at an extremely high rate, up to about twenty times greater than normal, requiring venting of large quantities of carbon monoxide vapor after a relatively short interval to prevent rupture of the container. In such situations, it is more difiicult, and sometimes impossible, to locate the transport at an isolated area before the venting becomes necessary. A more serious situation exists with respect to storage containers for 3,608,324 Patented Sept. 28, 1971 liquefied carbon monoxide permanently located at the site of the user. While continuous withdrawal of carbon monoxide from the container ordinarily precludes the necessity of venting carbon monoxide vapor resulting from normal heat leak into the container, in the event of loss of insulation efficiency it would be necessary to vent large quantities of carbon monoxide vapor at the site of the user.

The present invention provides a novel method and apparatus which overcomes the foregoing problems by converting hazardous carbon monoxide vapor into carbon dioxide vapor that may be discharged into the atmosphere with absolute safety as may be required in accordance with the internal pressure of the container.

DESCRIPTION OF THE DRAWINGS In the drawings, in which similar reference characters denote similar elements throughout the several views:

FIG. 1 is a diagrammatic illustration of an embodiment of the present invention adapted particularly for use with relatively small capacity containers, and

FIG. 2 is a diagrammatic illustration of another embodiment of the present invention adapted particularly for use with large capacity containers.

DETAILED DESCRIPTION The embodiment of the invention shown in FIG. 1 is disclosed in combination with a container 10 for liquefied carbon monoxide gas which may be of conventional construction including an inner vessel 11, a spaced outer vessel 12 to provide an intervening space 13 filled with suitable insulation and maintained under a relatively high vacuum. As shown, the inner vessel 11 is substantially filled with liquid carbon monoxide 14 leaving a vapor space 15 of carbon monoxide vapor, a valved conduit 16 or other suitable means being provided for introducing into and withdrawing from the container liquid carbon monoxide.

The novel arrangement provided by the present invention for effecting safe venting of carbon monoxide vapor from the container 10 includes a heat exchange device 17, a valve 18, an air inspiration device 19, and a catalytic reactor 20. The heat exchange device 17 has one end connected by conduit 21 to the vapor space 15 of the vessel 11 and functions to warm the relatively cold carbon monoxide vapor withdrawn from the vessel; the heat exchange device 17 may comprise a finned coil exposed to ambient air. The other end of the heat exchange device 17 is connected through the valve 18 and conduit 22 to an inlet port of the air inspiration device 19. The valve 18 is actuated by a pressure responsive element 23 to move the valve to open position when the pressure of the carbon monoxide vapor in the space 15 exceeds a predetermined value. The air inspiration device 19 may be of conventional construction including a first input port and an output port located in substantial linear flow alignment and a second input port located in angular or coaxial relation thereto. The conduit 22 is connected to the first input port, the output port is connected by conduit 24 to the catalytic reactor 20 and a conduit 25, open to the atmosphere, is connected to the second input port. The air inspiration device 19 operates in a conventional manner to deliver to the conduit 24 a mixture of carbon monoxide vapor and air in a ratio determined by the characteristics of the device. The catalytic reactor 20 includes a plurality of tubes 26 communicating between an inlet manifold 27, to which the conduit 24 is connected, and an outlet manifold 28 to which is connected a conduit 29 open to the atmosphere. The catalytic reactor may be provided with a plurality of external heat exchange fins 30 for cooling purposes. The tubes 26 contain a catalyst for efiecting oxidation of the carbon monoxide to carbon dioxide. Hopcalite, manganese dioxide supported on carbon, is a suitable catalyst; such catalyst being capable of catalytically oxidizing carbon monoxide to carbon dioxide containing no more than ppm. carbon monoxide. This catalyst is self-starting within the temperature ranges that may be involved and does not require regeneration. The air inspiiating device 19 is designed to provide a carbon monoxide-air mixture rich in air, specifically having a percentage of air greater than the stoichiometric ratio to insure complete oxidation of the carbon monoxide. The stoichiometric ratio of the carbon monoxide-air reaction is about 29% carbon monoxide and 71% air and it is preferred that the air inspiration device 19 produce a carbon monoxide-air mixture containing 25% carbon monoxide. Conventional gas inspiration devices may be designed to provide a carbon monoxide-air mixture of such ratio for a wide range of carbon monoxide vapor flow rates below that critical flow rate above which the flow is substantially constant. The cold carbon monoxide vapor withdrawn from the vessel preferably is warmed in the heat exchange device 17 at least to within 10 F. of ambient temperature to minimize the formation of ice or the condensation of moisture in the inspiration device even in the presence of moisture saturated air.

In operation, liquid carbon monoxide at atmospheric pressure and its liquefaction temperature is introduced into the container 10 to fill the container to its maximum liquid capacity and the filling system, such as valved conduit 16, is closed. Thereafter, due to the fact that the insulating action of insulation 13 is necessarily less than ideal, the liquid carbon monoxide will rise in temperature and the internal pressure in vessel 11 will gradually increase. The pressure responsive valve actuator 23 is set to open the valve 18 when the pressure in the vapor space 15 exceeds a predetermined value such as 30 p.s.i.g., the latter pressure being below the maximum operating design pressure of the container. When the internal pressure of the container increases beyond 30 p.s.i.g. as a consequence of continuing normal temperature rise of the liquid carbon monoxide, the valve 18 opens and thereupon cold carbon monoxide vapor at about 292 F. flows from the vessel through conduit 21 and is warmed in heat exchange device 17 to about 60 F., i.e., within 10 F. of ambient temperature. This warmed gas is mixed with air in the inspiration device 19 to provide a carbon monoxide-air mixture containing carbon monoxide and the mixture flows through the catalyst in the tubes 26 of the catalytic reactor 20 to eifect oxidation of the carbon monoxide to carbon dioxide which is discharged to the atmosphere through conduit 29. The rate of flow of carbon monoxide vapor through the conduit 21 onto the reactor 20 is such as to maintain the internal pressure of the container at about p.s.i.g. If desired, the pressure actuator 23 may be set to close the valve 18 at a lower pressure, such as 25 p.s.i.g. for example, so that carbon monoxide vapor periodically flows through the conduit 18 onto the reactor 20. In any event, the quantity of catalyst in the reactor 20 is suflicient to oxidize completely the carbon monoxide. The inspiration device 19 is designed to maintain the mixture at about 25% carbon monoxide content for all rates of flow of carbon monoxide vapor which are largely determined by the liquid carbon monoxide capacity of the container. A catalytic reactor of reasonable size has the capacity for handling the flow of carbon monoxide vapor resulting from normal boil-off in large capacity containers such as containers transported by rail.

As mentioned above, the storage and transporting of liquid carbon monoxide presents a potential hazard of immense proportions in the event the container insulation system becomes ineffective by a loss of vacuum in the insulation space, for example. In such event, the rate of vaporization of liquid carbon monoxide in the container may be twenty times the normal rate of vaporization. Even so, for small containers having a liquid carbon monoxide capacity of 5000 gallons and less, the rate of carbon monoxide vapor generated under conditions in which the insulation space is under atmospheric pressure will be no greater than 20 standard cubic feet per minute and a single catalytic reactor of reasonable size may be used to elfect complete oxidation of carbon monoxide vapor resulting from abnormal and normal vaporization of the liquid carbon monoxide. For example, with the container 10 having a liquid carbon monoxide capacity of 5000 gallons, the rate of flow of carbon monoxide vapor withdrawn from the container to maintain the internal container pressure below 30 p.s.i.g. for normal liquid vaporization conditions is about 1 standard cubic foot per minute; however, should the vacuum in the insulation space he lost, it would be necessary to withdraw carbon monoxide vapor at a rate of about 16 standard cubic feet per minute. A reactor 20 having the catalytic capacity to oxidize carbon monoxide vapor at a rate of 16 standard cubic feet per minute would not be of unreasonable size and the air inspiration device 19 may be designed to deliver a carbon monoxide-air mixture containing 25% carbon monoxde for all rates of flow of carbon monoxide vapor for 1-6 standard cubic feet per minute. For containers having greater liquid carbon monoxide capacity, it is not practicable to provide a single catalytic reaction means and a single air inspiration device because of the large quantity of carbon monoxide vaporization in abnormal situations such as damage to the contaner insulation system.

The embodiment of the invention shown in FIG. 2 is provided for use with containers of large liquid capacity. As shown, a conduit 40 is joined to the conduit 22 and connected to a valve 41 controlled by a pressure responsive means 42. The valve 41 is connected by conduit 43 to a plurality of air inspiration devices 44, 45 and 46, each of which may be similar to the device 19 of FIG. 1. The output ports of the inspiration devices 44, 45 and 46 are connected to catalytic reactors 47, 48 and 49, respec- Y tively; the reactors 47, 48 and 49 may be similar to the catalytic reactor 20 and are provided with discharge conduits 50, 51 and 52, respectively. The pressure responsive valve actuator 23 is set to open the valve 18 at a first pretermined pressure such as 30 p.s.i.g. and the pressure operator 42 is set to open the valve 41 at a second higher predetermined pressure, such as 40 p.s.i.g., the latter pressure being below the maximum operating design pressure of the container. During periods of normal liquid carbon monoxide vaporization, the valve 18 is opened to withdraw carbon monoxide vapor from the container and maintain the container pressure not in excess of 30 p.s.i.g., the withdrawn carbon monoxide vapor being oxidized in the reactor 20, all in the manner described above in connection with FIG. 1. During such operation, the pressure in the container will not exceed the second predetermined pressure of 40 p.s.i.g. and the valve 41 remains closed. However, should the insulation system of the container be damaged, the liquid carbon monoxide will vaporize at a faster rate and the inspiration device 19 will not be capable of passing the higher rate of flow of carbon monoxide vapor required to maintain the container pressure at 30 p.s.i.g. Thus, the container pressure will increase and reach 40 p.s.i.g. to eifect opening of the valve 41. When the valve 41 opens, carbon monoxide vapor will flow through the conduit 43 to the inspiration devices 44, 45 and 46. The inspiration devices 44, 45 and 46 discharge to their respective catalytic reactors 47, 48 and 49 a carbon monoxide-air mixture containing 25% carbon monoxide and the carbon monoxide is oxidized to carbon dioxide in the catalytic reactors and vented as such to the atmosphere. The capacity and number of the high pressure catalytic reactors 47, 48 and 49 depends upon the liquid capacity of the container. In any event, the combined capacity of the low pressure catalytic reactor 20 and the high pressure catalytic reactors is suflicient to oxidize the total carbon monoxide vapor withdrawn from the container at the rate of flow required to maintain the container pressure not substantially greater than 40 p.s.i.g. under most severe adverse conditions resulting in maximum rate of liquid carbon monoxide vaporization. Thus, although three high pressure catalytic reactors 47, 48 and 49 are shown, it will be understood that a greater or less number may be employed depending for the most part on the liquid capacity of the container and the characteristics of the insulation system.

We claim:

1. Method of storing normally gaseous hazardous material in liquid phase at low temperature in an insulated container comprising the steps of maintaining a body of liquefied normally gaseous hazardous material under relatively low pressure and at low temperature in an insulated container and sealing the container so that vaporization of the liquefied material in the container increases the pressure of the liquefied material in the container to a predetermined level,

withdrawing hazardous vapor from the container when the pressure in the container exceeds a predetermined value to maintain the pressure of the liquefied material in the container at a level not greater than the predetermined value,

warmingthe withdrawn hazardous vapor,

passing the warm hazardous vapor along a first path and mixing the warm hazardous vapor with moisturecontaining air to provide a first mixture of hazardous vapor and said air, the hazardous vapor bein warmed in the warming step to a temperature to minimize formation of ice and condensation of moisture when the hazardous vapor is mixed with moisture-containing air,

oxidizing the hazardous vapor of the first mixture,

and

discharging the oxidized hazardous vapor of the first mixture to the atmosphere.

2. Method of storing normally gaseous hazardous material as defined in claim 1 in which the hazardous vapor of the first mixture is oxidized by flowing the mixture through a zone containing a catalyst which effects oxidation of the hazardous vapor.

3. Method of storing normally gaseous hazardous material as defined in claim '1 in which the withdrawn hazardous vapor is warmed at least to within 10 F. of the temperature of the air mixed with the hazardous vapor.

4. Method of storing normally gaseous hazardous material as defined in claim 1 in which the mixture of hazardous vapor and air includes a percentage of hazardous vapor less than the percentage of hazardous vapor in a stoichiometric mixture of hazardous vapor and air.

5. Method of storing normally gaseous hazardous material as defined in claim 1 in which the normally gaseous hazardous material comprises carbon monoxide, and

in which the catalyst is Hopcalite.

6. Method of storing normally gaseous hazardous material as defined in claim 1 in which the normally gaseous hazardous material comprises carbon monoxide,

the withdrawn hazardous vapor is warmed at least to within 10 F. of ambient temperature,

the hazardous vapor-air mixture contains air in stoichiometric excess, and

in which the oxidation is catalyzed utilizing a catalyst which is self-starting and does not require regeneration.

7. Method of storing normally gaseous hazardous material in liquid phase at low temperature in an insulated container comprising the steps of maintaining a body of liquefied normally gaseous hazardous material under relatively low pressure and at low temperature in an insulated container and sealing the container so that vaporization of the liquefied material in the container increases the pressure of the liquefied material in the container to a predetermined level,

withdrawing hazardous vapor from the container when the pressure in the container exceeds a predetermined value to maintain the pressure of the liquefied material in the container at a level not greater than the predetermined value,

warming the withdrawn hazardous vapor,

passing the warm hazardous vapor along a first path and mixing the warm hazardous vapor with air to provide a first mixture of hazardous vapor and air,

oxidizing the hazardous vapor of the first mixture,

discharging the oxidized hazardous vapor of the first mixture to the atmosphere,

passing warm hazardous vapor withdrawn from the container along a second path when the pressure of the liquefied material in the container exceeds a second predetermined value greater than the first predetermined value,

mixing hazardous vapor of the second path with air to provide a second mixture of hazardous vapor and air,

oxidizing the hazardous vapor of the second mixture,

and

discharging the oxidized hazardous vapor of the second mixture to the atmosphere.

8. Method of storing normally gaseous hazardous material as defined in claim 7 in which the hazardous vapor of the second mixture is oxidized by flowing the second mixture through a zone containing a catalyst which effects oxidation of the hazardous vapor.

9. Method of storing normally gaseous hazardous material as defined in claim 7 in which the hazardous vapor of the second mixture is oxidized in a plurality of zones.

.10. Apparatus for storing normally gaseous hazardous material in liquid phase at low temperature comprising an insulated container for low pressure storage of liquefied normally gaseous material at low temperature,

means for introducing liquefied gaseous material into the container and for sealing the container,

a heat exchange device,

a gas inspirating means having an inlet port, a suction port communicating with the atmosphere and a discharge port,

conduit means for withdrawing vapor from the container and flowing the withdrawn vapor through the heat exchange device to the inlet port of the gas inspirating means,

a catalytic reactor having an inlet and an outlet connected to the atmosphere.

means connecting the discharge port of the gas inspirating means to the inlet of the catalytic reactor,

means responsive to a first pressure within the container for controlling flow of vapor through the conduit means,

a second gas inspirating means having an inlet port, a suction port communicating with the atmosphere and a discharge port,

oxidizing means connected to the discharge port of the second gas inspirating means, and

inspirator means. 11. Apparatus as defined in claim 10 in which the oxidizing means comprises a catalytic reactor.

References Cited UNITED STATES PATENTS 2,760,343 8/1956 Reed 62--5O 8/1926 Mase 23-288X 10 2,942,932 6/1960 Elliott 232-88X 3,006,153 10/1961 Cook 6248 3,197,287 7/1965 Innes et a1. 23288 3,490,878 1/ 1970 Russell 23-288 ALBERT W. DAVIS, JR., Primary Examiner US. Cl. X.R. 

